PIEZOELECTRIC RESONATOR AND PIEZOELECTRIC FILTER

摘要

A piezoelectric resonator is obtained that is capable of having a reduced size and thickness thereof and that is less prone to having a spurious component occurring in a mode at which it propagates in a piezoelectric thin film at a range higher than a resonant frequency. A piezoelectric resonator includes a laminated thin film having a first thin film portion supported by a substrate 2 and a second thin film portion separated from a first main surface of the substrate and acoustically isolated. The second thin film portion of the laminated thin film includes a piezoelectric thin film 5, a first electrode 12 disposed on the upper surface of the piezoelectric thin film, and a second electrode 13 disposed on the lower surface of the piezoelectric thin film and being larger and thicker than the first electrode. The piezoelectric resonator further includes a mass adding film 11 disposed around the first electrode 12 and on at least one part of a region outside the periphery of a piezoelectric vibrating portion where the first and second electrodes 12 and 13 overlap each other with the piezoelectric thin film 5 disposed therebetween. The second electrode 13 is formed, in plan view, so as to extend beyond the piezoelectric vibrating portion to a region at which the mass adding film 11 is disposed.